Gear-type rotary machine

ABSTRACT

A gear-type rotary machine for transport of liquids or for compression or expansion of gases comprises a housing accommodating two mating gear-shaped rotors whose shafts are preferably driven by externally mounted torque transmitting gears in such a way that the teeth of rotors are out of actual metallic contact with each other. The teeth of each rotor include two sets of smaller teeth alternating with one or more larger teeth, but all teeth of each rotor have a common pitch circle.

United States Patent 172] lnventor Erich Martin Kirchenleite 4, 8021 lcking, Germany [211 App]. No. 818,355 [22] Filed Apr. 22, 1969 [45] Patented Apr. 13, 1971 [54] GEAR-TYPE ROTARY MACHINE 5 Claims, 1 Drawing Fig.

[52] US. Cl 418/205 [51] Int. Cl F010 1/18 [50] Field of Search 103/126, 126 (TO);230/141; 123/12;9l/87, 89;418/205 [56] References Cited UNITED STATES PATENTS 744,050 11/1903 Comstock 91/87 953,328 3/1910 Geer 91/87 1,184,650 5/1916 lngraham 123/12 ooi ew 3,214,907 1 1/1965 Martin 123/12 FOREIGN PATENTS 15,140 11/1887 Great Britain 91/87 1,163,213 4/1958 France 103,126(TO) Primary Examiner-Carlton R. Croyle Assistant ExaminerWilbur J. Goodlin Attorney-Michael S. Striker GEAR-TYPE RUIARY MACHINE BACKGROUND OF THE INVENTION The present invention relates to improvements in machines for conveying and/or compressing or expanding gaseous or liquid fluids. More particularly, the invention relates to improvements in rotary pumps or motors. Still more particularly, the invention relates to improvements in geartype rotary pumps or motors.

Many types of rotary pumps and motors are known for use as a means to efiect expansion, compression and/or transport of gaseous and liquid fluids. Such rotary machines include lobe pumps such as Roots blowers, screw pumps including Quimby pumps, pumps or motors with oval gears and geartype rotary pumps or motors. It was also proposed to employ conventional gear-type rotary machines as internal combustion engines; however, all such engines are still in an early stage of development.

A drawback of conventional rotary machines is that the gear teeth, threads, lobes or otherwise configurated projections of their rotors define with the housing a large number of relatively small compartments. In the case of compressors, such compartments serve for transport of fluids from the inlet port to the outlet port of the housing and are a cause of undesirable noises which develop when a compartment begins to communicate with the compression chamber. This is due to the fact that compressed fluid (particularly gas) suddenly penetrates from the compression chamber into an oncoming compartment and thereby creates considerable noise. The situation is reversed in rotary gear-type motors, i.e., the noise is generated because compressed gas flows from the compartments into the outport. In all presently known geartype rotary machines, screw pumps, lobe pumps and blowers and analogous apparatus, the interior of the pressure tank and of the pressure line forms part of the compression chamber. The spreading of pressurized fluid from a relatively large compression chamber into oncoming compartments between the housing and the teeth, threads or lobes contributes significantly to energy requirements of such machines because the rotors must be continuously driven with a force which must overcome the maximum pressure in the compression chamber. Losses due to slippage (backflow) of pressurized fluid through clearances between the rotors on the one hand and the rotors and housing on the other hand are considerable. Another important cause of slippage is that the gears, lobes or screws must always be rotated against the maximum compression chamber pressure. In gear-type rotary motors which are used for compression of air, the equalization of pressures must take place between the surrounding atmosphere and the compartments in which the air is conveyed during compression, and no expansion of conveyed fluid can take place during transport from the inport to the outport of the housing.

Similar problems arise in rotary piston machines which are utilized for transport of gaseous fluids. Proposals to use such .machines for transport of gases include the provision of smooth-surfaced or toothed cylindrical drums (drive gears) which carry prismatic fluid-displacing bodies. The complementary rotors are provided with suitable recesses or spaces for such prismatic bodies. It was found that the just described machines are incapable of serving for compression .of gases or as thermal engines due to heat expansion of their rotary parts. If the rotors of such machines are provided with teeth, they generate excessive noise for reasons which were explained hereinbefore.

SUMMARY OF THE INVENTION An object of the invention is to provide a novel and improved gear-type rotary machine which can be utilized as a pump, compressor, motor or internal combustion engine.

Another object of the invention is to provide a gear-type rotary machine which generates little noise, whose energy requirements are lower than the energy requirements of lobe pumps, screw pumps and other presently known rotary machines, and which can be utilized for transport, compression or expansion of hot, cold and/or burning gaseous fluids and/or steam, or as a means for transporting or pumping liquid fluids.

A further object of the invention is to provide a gear-type rotary pump, motor or internal combustion engine wherein the losses due to slippage from the discharge side back to the suction side are minimal and which can operate properly without piston rings, packing strips or other types of costly and complicated sealing devices.

An additional object of the invention is to provide a machine which can be operated at a speed considerably exceeding the speed of presently known gear-type or analogous rotary pumps, wherein the wear on the rotors can be reduced to a minimum, and wherein the rotors require no lubrication so that the transported or treated fluid can be completely free of oil.

The invention is embodied in a rotary gear-type machine which is not utilized for transmission of torque but exclusively for transporting and/or changing the pressure (i.e., expansion of compression) of fluids. The machine comprises a housing defining a chamber provided with fluid admitting port means (inport) and fluid-evacuating port means (outport), a pair of mating gears rotatably accommodated in the chamber of the housing, and means for rotating at least one of the gears. Each of the gears includes several sets of differently dimensioned teeth (i.e., teeth having different moduli) but all teeth of each gear have a common pitch circle. In accordance with a presently preferred embodiment, each gear comprises teeth of a smaller first size or modulus and teeth of a larger second size or modulus. Savings in initial cost of the machine can be achieved if the machine employs a pair of congruent gears.

The machine is preferably further provided with movable valve means installed in the housing in the region of at least one of the port means, for example in the outport, to regulate the flow of fluid through the one port means. The valve means may comprise a rotary valve and means for rotating the valve in synchronism with the gears.

An additional feature of my invention resides in that the gears can be rotated in such a way that their teeth are held out of metallic contact with each other to thereby reduce the wear and eliminate the necessity of lubrication. This can be achieved by mounting each gear on a shaft which is journaled in the housing and by employing externally mounted torque transmitting gears arranged to rotate one of the shafts in one direction in response to rotation of the other shaft in the opposite direction, or vice versa.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved gear-type rotary machine itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a sectional view of a gear-type rotary machine which embodies the invention and is assumed to be utilized as a compressor for gaseous fluids.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The drawing shows a machine which comprises a housing I The points of transition between the teeth 6-7, 78, 8-9, 9- 6 are located onthe pitchcircle 4 and are respectively indicated at 14, 15, 16, 17. Analogously, the points of transition between the teeth 10-11, 11-12, 12-13, 13-10 are located on the pitch circle and are respectively indicated at 18, 19, 20, 21. The gears 2, 3 are congruent and of identical size and shape; this reduces the manufacturing cost.

For example, the illustrated machine can be utilized as a compressor and each of its gears 2, 3 can have a pitch diameter of 100 millimeters. The modulus of smaller teeth 6, 8, 10, 12 can equal one, and the modulus of larger teeth 7, 9, 11, 13 can equal 10. These gears are assumed to be located in a common plane and each thereof can be provided with two groups of 40 smaller teeth alternating with one larger tooth. Thus, and referring to gear 2, it may comprise 40 teeth 6, one tooth 7, 40 teeth 8 and one tooth 9. The four groups of teeth (a total of 82 teeth) form a complete annulus. It is clear that the number of teeth in each group can be varied almost at will; for example, each gear may have two groups of 30 smaller teeth each (modulus one) alternating with two groups of larger teeth of two teeth each (modulus The diameters of gears 2, 3 may be less than or may exceed 100 millimeters, and each of these gears may be very thin or of considerable or medium axial length.

lf desired, the gear 2 can drive the gear 3 or vice versa. HOwever, it is equally possible to drive the shaft 28 by a suitable motor and to rotate the shaft 29 by a drive gear (not shown) mounted on the shaft externally of the housing 1 and driving a second external gear (not shown) on the shaft 29, or vice versa. An advantage of such external gears is that they perform exclusively (or almost exclusively) a control function and that the working gears serve exclusively to transport and compress or expand gaseous and/or liquid fluids. Torque is transmitted from the external drive gear to the external driven gear so that the working gears 2, 3 are not subjected to any periodically recurring stresses which arise in lobe pumps or other conventional rotary machines wherein the fluid transporting or compressing gears, lobes or screws must also transmit torque. When the machine of the present invention utilized external torque transmitting gears, the teeth of the working gears 2, 3 need not actually touch each other so that these gears have no metallic contact and therefore require no lubrication which is of considerable advantage in many instances. For example, if the improved machine is utilized as an internal combustion engine, the working gears require no lubrication if the torque is transmitted by external gears; thus, compressed air and combustion products need not contain any oil or other lubricant. This saves expenses for separation of oil from transported fluids. Another advantage of such machines wherein the teeth of working gears are not in actual metallic contact is that the danger of explosion and poisoning or other contamination of transported fluids is eliminated or reduced to a minimum. Furthermore, the wear on the gears is practically nil. Proper lubrication of externally mounted driving and driven gears reduces the wear on such gears to a minimum.

Another important advantage of the improved machine is that the space between the nonmating gears and the portions of the surrounding housing 1 need not be subdivided into a large number of small compartments. In conventional machines which utilize working gears each of which has a single set of teeth of identical modulus, the tooth spaces between the roots and top lands of teeth which are adjacent to the housing constitute discrete compartments. in the illustrated machine, the two working gears 2, 3 define with the housing 1 a few relatively large compartments 22, 23 wherein the fluid is conveyed from the inport 31 to the outport or compression chamber 27. Thus, the frequency at which the transported fluid expands when a compartment 22 or 23 begins to communicate with the outport 27 is reduced to a fraction of the frequency in conventional machines whereby the improved machine produces less noise. The same holds true when the improved machine is compared with a conventional screw compressor. Another advantage of relatively large compartments 22, 23 is that the machine can be provided with a built-in regulating valve, for example, with a rotary regulating valve 24. This valve rotates about the axis of a shaft 25 and is driven at the exact angular speed of the gears 2, 3. lts purpose is to control evacuation of compressed fluid from the outport 27. The valve 24 is of particular advantage when the machine is utilized as a compressor because it contributes to a substantial reduction in energy requirements, to a reduction of noise and to a reduction of losses due to slippage (backflow) of fluid. Thus, the energy of compressed gaseous fluids can be utilized with a much greater efficiency than in presently known machines and the so-called gap or clearance losses are reduced to a minimum.

Such clearance losses can be further reduced by injecting water (or oil if the presence of oil in the outflowing fluid is of no consequence). Injection of water to reduce clearance losses is particularly advantageous because a certain amount of water is invariably liberated during compression of fluids. Water can be injected or pumped between the major surfaces (side surfaces) of the gears 2, 3 and the adjoining sidewalls of the housing 1. Such water serves as a coolant and as a means for displacing air. Since the compression of fluid is accompanied by generation of substantial amounts of heat, the injected water is converted into steam upon entry into the compartments 22, 23; thus, the regulating valve 24 discharges a mixture of air and steam whereby a portion of such mixture remains in the outport 27. When a compartment 22 or 23 begins to communicate with the outport 27, pressure in the outport drops suddenly, especially since the steam in outport 27 is condensed to water. The outport 27 is not comparable to the so-called dead space or cylinder clearance of piston pumps or compressors because no backfiring can take place therein. Such backfiring exerts an undesirable influence on the volumetric efficiency of conventional machines. Clearance losses are not considered here.

lnjection of water between the side faces of gears 2, 3 and the adjoining sidewalls of the housing 1 is of particular advantage when the improved machine is utilized as an internal combustion engine. Water which is injected during combustion effects considerable increase in the volume of fuel to thereby liberate substantial driving forces. Water hammer or water shock which could cause damage to or destruction of an internal combustion engine cannot develop as a result of water injection between the housing 1 and gears 2, 3.

It was found that the improved machine is the first of its type which can be used effectively as an internal combustion engine. The provision of larger and smaller teeth on each of the working gears 2, 3 insures that thermal expansion of one gear is compensated for by thermal expansion of the other gear. Such equalization of thermal expansion at elevated temperatures is desirable because the center distance of shafts 28, 29 (whose bearings are located without the range of elevated temperatures) is constant.

If the teeth 6-9 and 10-13 on the working gears 2, 3 are to provide a labyrinth seal between the inport 31 and outport 27, the automatic self-cleaning action of such teeth is of added importance. Thus, any deposits of foreign matter which settle on the flanks of teeth 6-13 are loosened while the gears 2, 3 rotate and the loosened deposits are ultimately ejected by centrifugal force to thereby reduce the likelihood of jamming.

The lead line of numeral 30 denotes the point or region where the diametral passage 26 of the regulating valve 24 begins to communicate with the outport 27 to connect the latter to a pressure line, not shown, when the shaft 25 rotates. As stated before, the shaft 25 of the valve 24 is driven at the exact speed of the shafts 28, 29.

It was found that the mechanical stability of the improved machine exceeds considerably the stability of lobe pumps and like rotary machines. Therefore, the gears 2, 3 can be driven at a high speed to increase the output and/or compression without necessitating any increase in dimensions of the machine. The maximum diameters of lobes in an equivalent Roots blower exceed considerably the diameters of my working gears 2, 3. Moreover, constrictions of lobes in a Roots blower and repeated changes in pressure cause such machines to vibrate which in turn renders them unsuited for a large number of applications. For example, Roots blowers cannot be used as internal combustion engines.

The improved machine also exhibits several important advantages over conventional screw-type compressors. The manufacture of working gears 2, 3 is simpler and less expensive and they are not prone to vibrate in use. Vibrations develop in screw compressors as a result of flexing of their screws; therefore, the shafts of such screws must be journaled in bearings which permit swiveling movements of screws. Even though the flexing of shafts in a screw compressor is not as pronounced as the flexing of shafts in a Root's blower, it is much more pronounced than the flexing of shafts 28, 29 in the present machine. Consequently, the machine of my invention can effect stronger compression of fluids (i.e., a compression which exceeds substantially the compression achievable in a screw compressor) and its shafts can be mounted in simpler and less expensive bearings. It is to be noted here that machines operating on the principle of screw compressors are not suited for use as internal combustion engines. In contrast to such screw compressors, the machine of the present invention can convert pressure into rotary movement without any deflection of fluids which renders it particularly suited for use as an internal combustion engine. Furthermore, the clearances (which are the main cause of slippage) are much narrower than in screw compressors or in lobe pumps, especially in the region of the shafts 28, 29. It is well known that the smallest (shortest) clearance lengths are located in the region of the smallest motion of a lobe pump, i.e., close to the shaft, which causes a substantial increase in clearance losses. Another advantage of the improved machine over lobe pumps is that the root circles of the smaller teeth are more distant from the axes of shafts so that the path for slippage is longer and hence offers a greater resistance to backflow of fluids. The large number of smaller teeth produces a turbulence which also impedes slippage.

The teeth of the gears 2, 3 can have any suitable profile, such as an involute of a circle or a cycloid curve. It is also clear that the profile of larger teeth need not be identical with the profile of smaller teeth.

The gear-type rotary machine of my invention should not be confused with conventional gearings which are used for transmission of torque. The working gears or rotors 2, 3 of my machine are used for transport and/or compression or expansion of gaseous or liquid fluids. It was found that the use of such machines for transport and/or change in pressure of fluids brings about surprising and unexpected advantages and novel effects which are not suggested when gears with several types or sizes of teeth are utilized only for transmission of torque. Thus, and in contrast to screw-type compressors and pumps wherein steam and/or gases undergo compression during axial transport, the improved machine transports fluids only in radial direction. This insures shorter slippage paths and reduces the energy requirements of the machine. Moreover, and as mentioned above, the working gears of my machine can be produced at a cost which is but a fraction of the cost of screws for a screw compressor and the rotors of lobe pumps or the like.

Furthermore, and while a screw compressor cannot operate with valves, the improved machine can be used with or without valve means. The regulating valve 24 facilitates more accurate regulation of the outflow of pressurized or compressed fluids and contributes to higher output of the machine. If desired, the inport 31 can be provided with a second regulating valve or such regulating valve can be used instead of the valve 24.

Still another advantage of my machine is that it need not employ piston rings, sealing strips and/or other types of packings which are used to seal clearances in conventional rota machines. Since the machine can be operated at high spee s, damming of gases along the edges of revolving rotors is very effective as a seal for clearances.

When used for pumping of liquid fluids, the improved machine operates with an efficiency which exceeds that of conventional gear-type rotary pumps because the amounts of so-called squeeze liquid are much lower.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art.

What is claimed as new and desired to be protected by Letters Pat. is set forth in the appended claims.

lclaim:

l. A rotary machine for transporting and/or changing the pressure of fluids, comprising a housing defining a chamber provided with fluid-admitting port means and fluid-evacuating port means; a pair of constantly and accurately mating gears rotatably accommodated in said chamber, each of said gears including several sets of differently dimensioned teeth having a common pitch circle, said teeth including teeth of smaller first size and at least one tooth of a larger second size; means for rotating said gears, comprising a pair of shafts each journaled in said housing and each coaxially secured to one of said gears, and torque transmitting gears mounted on said shafts externally of said housing for rotating one of said shafts in one direction in response to rotation of the other shaft in the opposite direction, said torque transmitting gears being arranged to maintain said first mentioned gears out of metallic contact with each other; rotary valve means provided in said housing in the region of at least one of said port means to regulate the flow of fluid through said one port means; and

means for rotating said valve means in synchronism with said first mentioned gears.

2. A rotary machine as defined in claim 1, wherein said gears are congruent.

3. A rotary machine as defined in claim 1, wherein said gears are of identical size and shape.

4. A rotary machine as defined in claim 1, wherein the teeth of each of said gears comprise several sets of smaller teeth and several larger teeth, said sets of smaller teeth being separated from each other by at least one of said larger teeth.

S. A rotary machine as defined in claim 4, wherein said larger teeth define with said housing a relatively small number of relatively large compartments wherein the fluid is transported from said fluid admitting port means to said fluid evacuating port means in response to rotation of said gears. 

1. A rotary machine for transporting and/or changing the pressure of fluids, comprising a housing defining a chamber provided with fluid-admitting port means and fluid-evacuating port means; a pair of constantly and accurately mating gears rotatably accommodated in said chamber, each of said gears including several sets of differently dimensioned teeth having a common pitch circle, said teeth including teeth of smaller first size and at least one tooth of a larger second size; means for rotating said gears, comprising a pair of shafts each journaled in said housing and each coaxially secured to one of said gears, and torque transmitting gears mounted on said shafts externally of said housing for rotating one of said shafts in one direction in response to rotation of the other shaft in the opposite direction, said torque transmitting gears being arranged to maintain said first mentioned gears out of metallic contact with each other; rotary valve means provided in said housing in the region of at least one of said port means to regulate the flow of fluid through said one port means; and means for rotating said valve means in synchronism with said first mentioned gears.
 2. A rotary machine as defined in claim 1, wherein said gears are congruent.
 3. A rotary machine as defined in claim 1, wherein said gears are of identical size and shape.
 4. A Rotary machine as defined in claim 1, wherein the teeth of each of said gears comprise several sets of smaller teeth and several larger teeth, said sets of smaller teeth being separated from each other by at least one of said larger teeth.
 5. A rotary machine as defined in claim 4, wherein said larger teeth define with said housing a relatively small number of relatively large compartments wherein the fluid is transported from said fluid admitting port means to said fluid evacuating port means in response to rotation of said gears. 